From fcf6ccd77107d64301a30f8d66583dbccd1ac217 Mon Sep 17 00:00:00 2001
From: Andreas Kling <kling@serenityos.org>
Date: Sun, 26 Dec 2021 14:31:45 +0100
Subject: [PATCH] Kernel: Make KernelRng not inherit from Lockable

This class was misusing the outdate Lockable template and didn't take
advantage of the lock/resource separation mechanism fully anyway.

Since the underlying PRNG has its own SpinLock, and we already use that
for synchronization everywhere anyway, we can simply remove the Lockable
inheritance from this class.
---
 Kernel/Random.cpp | 21 ++++++++++-----------
 Kernel/Random.h   |  7 ++-----
 2 files changed, 12 insertions(+), 16 deletions(-)

diff --git a/Kernel/Random.cpp b/Kernel/Random.cpp
index 1889245991..fedb562c19 100644
--- a/Kernel/Random.cpp
+++ b/Kernel/Random.cpp
@@ -30,7 +30,7 @@ UNMAP_AFTER_INIT KernelRng::KernelRng()
     bool supports_rdrand = Processor::current().has_feature(CPUFeature::RDRAND);
     if (supports_rdseed || supports_rdrand) {
         dmesgln("KernelRng: Using RDSEED or RDRAND as entropy source");
-        for (size_t i = 0; i < resource().pool_count * resource().reseed_threshold; ++i) {
+        for (size_t i = 0; i < pool_count * reseed_threshold; ++i) {
             u32 value = 0;
             if (supports_rdseed) {
                 asm volatile(
@@ -46,22 +46,22 @@ UNMAP_AFTER_INIT KernelRng::KernelRng()
                     : "=r"(value));
             }
 
-            this->resource().add_random_event(value, i % 32);
+            add_random_event(value, i % 32);
         }
     } else if (TimeManagement::the().can_query_precise_time()) {
         // Add HPET as entropy source if we don't have anything better.
         dmesgln("KernelRng: Using HPET as entropy source");
 
-        for (size_t i = 0; i < resource().pool_count * resource().reseed_threshold; ++i) {
+        for (size_t i = 0; i < pool_count * reseed_threshold; ++i) {
             u64 hpet_time = HPET::the().read_main_counter_unsafe();
-            this->resource().add_random_event(hpet_time, i % 32);
+            add_random_event(hpet_time, i % 32);
         }
     } else {
         // Fallback to RTC
         dmesgln("KernelRng: Using RTC as entropy source (bad!)");
         auto current_time = static_cast<u64>(RTC::now());
-        for (size_t i = 0; i < resource().pool_count * resource().reseed_threshold; ++i) {
-            this->resource().add_random_event(current_time, i % 32);
+        for (size_t i = 0; i < pool_count * reseed_threshold; ++i) {
+            add_random_event(current_time, i % 32);
             current_time *= 0x574au;
             current_time += 0x40b2u;
         }
@@ -71,7 +71,7 @@ UNMAP_AFTER_INIT KernelRng::KernelRng()
 void KernelRng::wait_for_entropy()
 {
     SpinlockLocker lock(get_lock());
-    if (!resource().is_ready()) {
+    if (!is_ready()) {
         dbgln("Entropy starvation...");
         m_seed_queue.wait_forever("KernelRng");
     }
@@ -80,7 +80,7 @@ void KernelRng::wait_for_entropy()
 void KernelRng::wake_if_ready()
 {
     VERIFY(get_lock().is_locked());
-    if (resource().is_ready()) {
+    if (is_ready()) {
         m_seed_queue.wake_all();
     }
 }
@@ -126,8 +126,7 @@ bool get_good_random_bytes(Bytes buffer, bool allow_wait, bool fallback_to_fast)
     if (can_wait && allow_wait) {
         for (;;) {
             {
-                MutexLocker locker(KernelRng::the().lock());
-                if (kernel_rng.resource().get_random_bytes(buffer)) {
+                if (kernel_rng.get_random_bytes(buffer)) {
                     result = true;
                     break;
                 }
@@ -136,7 +135,7 @@ bool get_good_random_bytes(Bytes buffer, bool allow_wait, bool fallback_to_fast)
         }
     } else {
         // We can't wait/block here, or we are not allowed to block/wait
-        if (kernel_rng.resource().get_random_bytes(buffer)) {
+        if (kernel_rng.get_random_bytes(buffer)) {
             result = true;
         } else if (fallback_to_fast) {
             // If interrupts are disabled
diff --git a/Kernel/Random.h b/Kernel/Random.h
index d2b9e96c7d..dc7ae70436 100644
--- a/Kernel/Random.h
+++ b/Kernel/Random.h
@@ -10,7 +10,6 @@
 #include <AK/Assertions.h>
 #include <AK/ByteBuffer.h>
 #include <AK/Types.h>
-#include <Kernel/Locking/Lockable.h>
 #include <Kernel/Locking/Mutex.h>
 #include <Kernel/StdLib.h>
 #include <LibCrypto/Cipher/AES.h>
@@ -120,7 +119,7 @@ private:
     Spinlock m_lock;
 };
 
-class KernelRng : public Lockable<FortunaPRNG<Crypto::Cipher::AESCipher, Crypto::Hash::SHA256, 256>> {
+class KernelRng : public FortunaPRNG<Crypto::Cipher::AESCipher, Crypto::Hash::SHA256, 256> {
     AK_MAKE_ETERNAL;
 
 public:
@@ -131,8 +130,6 @@ public:
 
     void wake_if_ready();
 
-    Spinlock& get_lock() { return resource().get_lock(); }
-
 private:
     WaitQueue m_seed_queue;
 };
@@ -168,7 +165,7 @@ public:
         SpinlockLocker lock(kernel_rng.get_lock());
         // We don't lock this because on the off chance a pool is corrupted, entropy isn't lost.
         Event<T> event = { read_tsc(), m_source, event_data };
-        kernel_rng.resource().add_random_event(event, m_pool);
+        kernel_rng.add_random_event(event, m_pool);
         m_pool++;
         kernel_rng.wake_if_ready();
     }